A sander is a power tool used to smooth surfaces or abrade away a surface layer of material or a coating on a surface. Sanders generally include an attachment point for attaching an abrasive material such as sand paper, and a drive mechanism that drives the attachment point into motion. Both the abrasive material and the drive mechanism can have many different forms. A drum sander, in particular a portable drum sander, generally includes a drive mechanism that drives the rotation of an output spindle, and a drum that includes an abrasive material. The abrasive material can be integral with the drum, or can be a separate piece that is mounted on the drum. The drum is mounted to and rotated by the output spindle, and the resulting rotation of the abrasive material forms a three-dimensional friction region that can be applied to a workpiece. Drum sanders are adapted for a wide variety of applications, such as sanding tight or hard to reach places.
Drums are generally tubular in shape. While drums having a shape that is somewhat varied from a generally tubular shape have been made, such as drums with a frustum or ellipsoid shape, the high rate of rotation generally limits that shapes that drums can take. As a result, one disadvantage with drum sanders is that drum sanders are generally not adapted to sanding surfaces with a complex contour. The generally tubular shape of the drum may not align with the complex contour, resulting in a flattening out of the features of the surface and a generally poor finish of the workpiece. As a result, drum sanders generally do not perform well when used on surfaces with a shape that varies along an extent of the surface.
Advances have been made in order to address some of these deficiencies. A flap-wheel drum includes a central drum and a plurality of flaps of abrasive material radiating outward from the central drum. The flaps are configured to flex, so that the diameter of the flap-wheel drum can effectively change in order to accommodate a changing surface shape. Flap-wheel drums, however, still exhibit the same type of flattening behavior as other drums when applied to a surface with a complex contour.
Therefore, a drum for a drum sander that can be applied to surfaces with a complex contour without flattening out the complex contour would be beneficial.